#include <iostream>

consteval int len(const char *src) {
    int i = 0;
    while (src[i] != '\0') {
        i++;
    }
    return i;
}

int main(int argc, char **argv) {
    constexpr int l = len("test of getting the length of this long string");
    std::cout << "len: " << l << "\n";
    return 0;
}

// compiles to: doesn't even include the string in the code!
/*

.LC0:
        .string "len: "
.LC1:
        .string "\n"
main:
        push    rbp
        mov     rbp, rsp
        sub     rsp, 32
        mov     DWORD PTR [rbp-20], edi
        mov     QWORD PTR [rbp-32], rsi
        mov     DWORD PTR [rbp-4], 46
        mov     esi, OFFSET FLAT:.LC0
        mov     edi, OFFSET FLAT:_ZSt4cout
        call    std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)
        mov     esi, 46
        mov     rdi, rax
        call    std::basic_ostream<char, std::char_traits<char> >::operator<<(int)
        mov     esi, OFFSET FLAT:.LC1
        mov     rdi, rax
        call    std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)
        mov     eax, 0
        leave
        ret

*/